During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as evaluating the production capabilities of formations intersected by the well bore. For example, after a well or well interval has been drilled, zones of interest are often measured or tested to determine various formation and fluid properties. These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production. The acquisition of accurate data from the well bore is critical to the optimization of hydrocarbon wells. This well bore data can be used to determine the location and quality of hydrocarbon reserves, whether the reserves can be produced through the well bore, and for well control during drilling operations.
The collected data is contained in a survey or “log,” then analyzed to determine one or more properties of the formation, sometimes as a function of depth. Many types of formation evaluation logs, e.g., mechanical, resistivity, acoustic and nuclear, are recorded by appropriate downhole instruments supported by a housing. The housing may include a sonde with the instruments and a cartridge with associated electronics to operate the instruments in the sonde. Such a logging tool is lowered into the well bore to measure properties of the formation. To reduce logging time, a combination of logging tools may be lowered in a single logging run.
Often, logging tools are lowered into vertical well bores by wireline. Gravity moves the logging tools into the well bore, and the wireline is used for electrical communication and support for pulling the logging tools out of the well bore. Logging deep, extended, deviated or horizontal wells can be problematic with wireline. The wireline provides no driving force for pushing, rather than pulling, logging tools further into the well bore. To log such well bores, tubulars such as coiled tubing or drill pipe transport logging tools into the well bore. Pipe, tubing, tubular and like terms may all be used to reference such a conveyance. In some cases, wireline logging tools are adapted for drill pipe deployment. The logging tools are coupled to the operational end of the tubular and may be extendable from the tubular.
Pipe conveyed well logging tools are relatively fragile as compared to the drill string from which they are deployed. Further, extendable well logging tools are exposed to the downhole environment. When a borehole is drilled, it is seldom smooth and regular. It has cave-ins, erosions, washouts, shales and clays that squeeze into the hole, ledges, protrusions and other rugosity. Wellbore debris is also present. As the pipe is moved downhole to convey the logging tool, wellbore debris can collect in the open end of the pipe, thereby plugging the tool deployment end. The debris can cause damage to the logging tools. The plugged opening can also cause unwanted adjustments of the expected distance between the extended logging tool and the drill pipe, thereby affecting the accuracy of the depth-dependent measurements and formation properties derived therefrom.
These and other limitations of the prior art are overcome by the embodiments and principles taught herein.